The overall goal of this proposal is to undertake an integrative, multi-level study of the social outcomes of childhood traumatic brain injury (TBI). The study is grounded in models and methods drawn from both the emerging field of social cognitive neuroscience and the study of social competence in developmental psychology/psychopathology. The study's specific aims are to: (1) characterize the social interactions and adjustment of children with TBI;(2) examine social information processing in children with TBI;(3) determine the integrity of brain regions and structures known to be vulnerable to TBI and implicated in social information processing;and (4) study the linkages among brain structures, social information processing, and social behavior and adjustment among children with TBI. The study will involve 8 to 12 year old children, 150 with moderate to severe TBI and 150 with orthopedic injuries not involving the head, in a cross-sectional, concurrent cohort research design. Participants will complete several assessments: (1) structural magnetic resonance imaging, to enable measurement of brain abnormalities in regions implicated in social cognition;(2) measures of social information processing;(3) direct observations of interactions with friends and unfamiliar peers;(4) measures of perceived social adjustment, as reported both by the participants and by their friends, classmates, parents, and teachers;and (5) measures of environmental variables, such as family functioning and parenting practices, that may act as risk or resilience factors in moderating the effects of TBI on social development. Data analyses will involve between-group comparisons to test hypotheses linked to Aims 1-3, and structural equation modeling of within-group associations to test hypotheses linked to Aim 4. The project will represent a major expansion of the existing knowledge base about the outcomes of childhood TBI, and will also provide insights into the neural and cognitive-affective substrates of social behavior more generally. Its methods and findings will be applicable to children with other insults to the central nervous system, as well as to healthy children. Thus, the project will contribute to our understanding of both normal and aberrant social development. Practically speaking, the study will further the development of methods for measuring impairments and disabilities in children with TBI, and in the long run should assist in identifying residual deficits and designing interventions to promote better social outcomes following childhood TBI. Public health relevance: Traumatic brain injury (TBI) is a leading cause of death and disability in youth under the age of 15, and therefore represents a major public health problem. Poor social outcomes are an important aspect of the morbidity associated with pediatric TBI. By helping to better understand social outcomes after childhood TBI, the study's findings may suggest ways to promote children's behavioral adaptation to the functional losses and disabilities that frequently occur after TBI.